In the reaction, 

Cr2O72- +14H+ + 6I- 2Cr3+ + 7H2O + 3I2,

Which element is reduced?

1. I

2. O

3. H

4. Cr

Subtopic:  Oxidizing & Reducing Agents |
 85%
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2Na2S2O+ I Na2S4O6 + 2NaI,

the oxidation state of sulphur in tha above reaction:

1. Decreases

2. Increases

3. Remain unchanged

4. None of the above

Subtopic:  Oxidizing & Reducing Agents |
 80%
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In the aluminothermic process, aluminium acts as:

1. an oxidising agent

2. a flux

3. a reducing agent

4. a solder

Subtopic:  Introduction to Redox and Oxidation Number |
 59%
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Disproportionation reaction(s) among the following is/are represented by -

1. Cl2 + 2OH- ClO- + Cl- + H2O

2. Cu2O(s) + 2H+ Cu2+ + Cu(s) + H2O

3. 2HCuCl2 waterDilution with Cu + Cu2+ + 4 Cl- +  2H+

4. All of the above

Subtopic:  Introduction to Redox and Oxidation Number |
 83%
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In a redox change, the oxidant K2Cr2O7 is always reduced to:

1. Cr5+

2. Cr4+

3. Cr3+

4. Cr2+

Subtopic:  Introduction to Redox and Oxidation Number |
 76%
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The reaction, 

3ClO-(aq)ClO3-(aq) + 2Cl-(aq)

is an example of:

1. oxidation reaction

2. reduction reaction

3. disproportionation reaction

4. decomposition reaction

 

Subtopic:  Introduction to Redox and Oxidation Number |
 87%
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Oxidation state of +1 for phosphorus is found in:

1. H3PO3 

2. H3PO4

3. H3PO2

4. H4P2O7

Subtopic:  Oxidizing & Reducing Agents |
 88%
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Which of the following reactions does not represent a redox change?

1. CaCO3 CaO + CO2

2. 2H2 + O2 2H2O

3. Na + H2 NaOH + \(\frac{1}{2}\)H2

4. MnCl3  MnCl2 + \(\frac{1}{2}\)Cl2

Subtopic:  Introduction to Redox and Oxidation Number |
 71%
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If H2S is passed through an acidified K2Cr2O7 solution, the colour of the solution:

a. will remain unchanged

b. will change to deep red

c. will change to dark green

d. will change to dark brown 

Subtopic:  Introduction to Redox and Oxidation Number |
 58%
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The oxidation number and covalency of sulphur in the sulphur molecule (S8) are respectively:

1. 0 and 2

2. +6 and 8

3. 0 and 8

4. +6 and 2

Subtopic:  Oxidizing & Reducing Agents |
 55%
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